The present invention relates to spray guns, and more particularly to the hand held type by which a liquid such as paint is sprayed by the action of compressed air that is delivered through the hollow handle of the spray gun to entrain and atomize the paint and dispense the atomized paint from a storage container associated with the spray gun through a nozzle toward an object to be sprayed with the paint.
In conventionally known paint spray guns high pressure compressed air arrives to the spray head of the gun to draw and atomize the paint from a container generally attached to the gun by means of a paint delivery tube and an adjustable or fixed nozzle. In the past the fact that a tremendous excess of atomized paint was sprayed into the atmosphere while painting and object was of no concern so the level of pressure of the pressurized air entering the gun was not considered so long as a sufficient amount was available to form an atomized quantity and pattern of the paint leaving the gun which was suitable for painting a desired object.
The thought of reducing the pressure of pressurized air for atomizing the paint leaving the gun nozzle was noted in U.S. Pat. No. 3,796,376 issued to inventor Irmgard O. W. Farnsteiner of Monte-Carlo, Monaco. In this patent the air volume is somewhat increased and the pressure is somewhat reduced to a lower than source level by means of a venturi built into the handle which mixed high pressure air with atmospheric air. With a built in system of the configuration of the reference, the pressure reducing and volume increasing system is not adaptable to conventional and existing spray guns. In order to take advantage of a venturi type pressuring reducing and volume maintaining configuration as taught by the Farnsteiner reference all of the existing paint spray guns must be discarded and replaced with a gun with a built in venturi system.
A further disadvantage of the spray gun of the above referenced patent is that the internal gun pressure still exceeds the spray gun operating pressures mandated by Federal, State and local government environmental standards which mandate less then ten pounds PSI at the nozzle.
A pending patent application which two of the inventors of the present invention are the co-inventors having Ser. No. 07/258,508 filed Oct. 17, 1988 teaches an improvement to volume of air at the nozzle and changes the configuration of the venturi built into the handle to comply with the above referenced environmental requirements.
In our above referenced co-pending application a spring biased ball valve is described for providing a positive pressure to the container of liquid to be sprayed and further for controlling the dispensing of liquid when the spray action is terminated.
The present invention is directed to providing a venturi assembly that is attachable to existing hand held spray guns which will allow these spray guns to comply with the above referenced environmental standards for paint spraying and a newly configured ball valve which eliminates the need for the spring bias which controls the exit of the internal gun pressure used to pressurize the container for delivering paint from the paint container into the nozzle.